This invention relates generally to building construction and more particularly to a metal roof truss therefore.
To reduce the costs of building construction, many approaches have been proposed in the past to utilize steel roof trusses. In U.S. Pat. No. 2,541,784 issued to H. S. Shannon, "C" or "U" shaped sections are used for the bottom chord member as well as the top chord members of a building truss. One problem with using just a "C" or "U" shaped section for all the chords is that unless extremely thick steel is utilized, the roof truss may not include enough rigidity to adequately support roof loading unless additional trusses are added.
Another roof truss arrangement is shown in U.S. Pat. No. 4,435,940 issued to Jeanne A. Davenport, et al. and a similar arrangement is described in U.S. Pat. No. 4,982,545 to Gustaf M. Stromback. In both of these prior truss arrangements, the horizontal, bottom chord section of a roof truss is formed from a U-shaped section of sheet steel. In the Stromback patent the ends of the legs of the U are tightly folded back to form a double thick edge. The top chords of both the Davenport and the Stromback patent are formed of inverted U-shaped sections having flanges projecting outwardly from the ends of each of the legs to provide greater rigidity.
One difficulty with both of those prior approaches to manufacturing of metal roof trusses is that different components are used for the bottom chords and the top chords resulting in two different fabrication lines or at least two different set ups for fabrication lines being required. Furthermore, two different stock items must be maintained in inventory. In addition, because of the flanges on the top chord members it is necessary to provide for cutting the flanges off at least one of the top chords at the apex of the truss.
One further problem which has occurred in the utilization of metal roof trusses is the difficulty of fastening roofing material to the flat surface of the truss members. When it is attempted to utilize power screws, it is quite common for the screw to wander on the flat steel surface.